JPH10217212A - Manufacture of ceramic formed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To settle the apprehension regarding the influence of flying an organic solvent to exhaust facilities and human bodies by a method wherein a crosslinkable water-soluble binder is employed. SOLUTION: As the crosslinkable water-soluble binder used for the slip casting of ceramic, a binder, which crosslinks ceramic casting slip through crosslinking reaction to a hardness enough high and substantially has a water solubility, is employed. The preferable solubility (= the weight of solute/the weight of a solution) is about 10%. The preferable binder is a mixture of a crosslinkable component and a crosslinker. As the crosslinkable component, a water-soluble epoxy-based resin such as glycidyl ether or the like is exampled. As the crosslinker, an amine-based compound is exampled. By employing a binder mainly made of a crosslinked body including the water-soluble epoxy- based resin and the amine-based compound, there is no apprehension regarding the exhaustion of an organic solvent and the influence to human bodies and a formation, in which no crack or the like develops even after the hardening through reaction and after the baking of a ceramic formed body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a ceramic molded body.

[0002] The cast molding of the present invention is suitably used for a product having a complicated shape or a thick wall shape, relates to a method capable of forming a net shape, and obtaining a molded body in an extremely short time as compared with the conventional cast molding.

[0003]

2. Description of the Related Art In recent years, ceramic parts having complicated shapes have been demanded for mechanical structural parts, decorative parts, electronic parts and the like which require heat resistance and durability.

[0004] These components often have complicated shapes according to the required high functions. Ceramics are excellent in heat resistance, durability, corrosion resistance, and abrasion resistance, but have a problem that it is extremely difficult to form or process into a complicated shape.

[0005] For this reason, various molding methods have been studied, and complicated shapes that could not be produced by die press or rubber press molding, such as cast molding, injection molding, extrusion molding and sheet molding, can be easily formed by near net shape. It has become.

[0006] Among them, the conventional casting method is a method in which a slurry is poured into a water-absorbent mold to form an inlaid layer, thereby obtaining a formed body. Although this method is inferior in productivity as compared with press forming and plastic forming, it is capable of forming a large and complicated shape, is inexpensive for forming equipment, and is suitable for small-quantity production. However, the conventional casting method has disadvantages such as wear and clogging caused by repeated use of the mold, resulting in a decrease in dimensional accuracy and cracks when the molded body is dried. . Therefore, a casting method in which an unsaturated polymer and a binder containing a cross-linked body containing a vinyl group or an acryl group as a main component are used as an organic binder to be mixed with the ceramic powder and the reaction hardening is performed is disclosed in JP-A-8-13.
No. 3844 has proposed this.

[0007]

However, since these organic binders are not water-soluble and are soluble only in organic solvents, there are concerns about the effects of the scattered organic solvents on the exhaust equipment and the human body, which poses a practical problem. Was.

[0008]

The object of the present invention can be basically achieved by the following constitution. That is, "a method for producing a ceramic molded body, characterized in that a crosslinkable water-soluble binder is used in the casting of ceramics."

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described in detail.

[0010] The crosslinkable water-soluble binder in the present invention is not particularly limited, and it is crosslinked to a hardness sufficient to cause a crosslinking reaction to sufficiently cure the slurry for casting of ceramics, and to be substantially formed. Any substance having water solubility may be used. Although not particularly limited, the solubility (= solute weight / solution weight) is preferably 10% or more, more preferably 30% or more. A single substance or a mixture may be used, but a mixture of a crosslinkable component and a crosslinking agent is preferred. The crosslinking component is not particularly limited, but a water-soluble epoxy resin can be exemplified, and the crosslinking agent can be an amine compound. That is, a preferred combination is a binder mainly composed of a crosslinked body containing a water-soluble epoxy resin and an amine compound,
The mixture of the binder and the ceramic powder may be filled in a molding die and cured by reaction to form a molded body.

The water-soluble epoxy resin of the present invention includes the most common types such as glycidyl ether, glycidyl ester, methyl glycidyl ether, cyclohexene oxide, and epoxidized polybutadiene. The glycidyl ether type cures smoothly even at room temperature. Therefore, it is suitable as a reaction curable resin.

It is preferable to use a commercially available polycarboxylic acid-based or polyacrylic acid-based dispersant.

As a curing agent for the epoxy resin, there is a compound having an amino group, a carboxyl group or a hydroxyl group, and an amine compound is particularly effective. Amine compounds include primary, secondary, and tertiary amines in which one, two, or three Hs of ammonia are replaced by hydrocarbons. Monoamine, depending on the number of amines in one molecule,
They are called diamines, triamines, and polyamines, and are further classified into aliphatic, alicyclic, and aromatic amines depending on the type of hydrocarbon. In the present invention, any amine compound can be used.

The curing of the epoxy resin with the amine-based curing agent is carried out by reacting the active hydrogen of the primary amine with the epoxy group.
An amine is formed and the secondary amine reacts with the epoxy group and cures. Further, the generated tertiary amine polymerizes the epoxy group.

In general, in order for a cured product to become a crosslinked polymer, the curing agent requires three or more active hydrogens in one molecule and two or more amino groups. The amount of the curing agent with respect to the epoxy resin is optimal when the epoxy group and the active hydrogen are equimolar. Actually, when the aliphatic and aromatic polyamines are equimolar, the cured product has a glass transition temperature, heat resistance, etc. Become the best. The curing speed by the amine differs depending on the type and amount of the amine and the type of the epoxy resin.

The epichlorohydrin condensate, which is a glycidyl ether type resin, is almost cured at room temperature by an aliphatic amine, but is hardened at room temperature by an aromatic amine.
Heat curing is required. When the blending amount does not increase or decrease more than the chemical equivalent, the apparent curing speed is faster as the amine amount is larger, and is slower as the blending amount is smaller. In practice, this can be used to adjust the curing speed.

The powder can be applied to all kinds of ceramics, but can be applied to fine ceramic raw materials, alumina, zirconia, mullite, silicon nitride, silicon carbide, and all of these composite ceramics, which have been considered difficult to cast and mold. . However, it is desirable that the raw material powder is well pulverized and dispersed in advance.

Pure water is used in an amount of 15 to 70 parts by weight based on 100 parts by weight of the ceramic powder. If the amount is less than 15 parts by weight, the viscosity of the slurry becomes high because the solvent is insufficient, and the slurry does not spread to the details of the mold, and the moldability is reduced. At 70 parts by weight, the water content is too high, and it is difficult to release after curing,
Also, the drying time becomes longer. Pure water is more preferably 25
When used in an amount of 50 parts by weight, a good slurry can be obtained. Further, it is preferable to use 2 to 10 parts by weight of a binder and 0.1 to 5 parts by weight of a dispersant with respect to 100 parts by weight of the ceramic powder.

The slurry thus prepared is sufficiently pulverized and mixed by a general pulverizer such as an attrition mill, a bead mill, and a ball mill. Preferably, the following curing agent is added to the binder in an amount of 1 to 4 parts by weight with respect to 10 parts by weight of the binder, and the mixture is further mixed for several minutes to several tens of minutes.

It is preferable that the slurry is taken out of the container of the pulverizer into another container and defoamed under vacuum at a reduced pressure of 10 torr or less for 5 to 60 minutes before pouring into the mold.
The method of casting is the same as the conventional casting method,
Perform at any of normal pressure.

In the cast molding of the present invention, since the molded body is solidified while retaining a considerable amount of water, if gypsum such as a conventional mold is used, water is absorbed from the slurry and the shape of the molded body is distorted or cracked. Therefore, it is extremely important to use a casting mold having no water absorption. It is preferable to use various plastics or metals for the mold material having no water absorption.

It is preferable to apply a release agent such as a silicon-based or fluorine-based release agent on the inner surface of the mold that comes into contact with the slurry in advance, since it is very easy to remove the mold.

In the reaction curing, since the curing agent is solidified at room temperature for 2 to 20 hours after injecting the curing agent, the mold is released when it has a certain degree of shape retention. As a guide, if the slurry does not drip even if the mold is inverted, the mold can be removed.

The ceramic molded body removed from the mold is
It is preferable to dry while humidifying or controlling the humidity so that the relative humidity is 30% to 70%. The reason for this is to prevent the molded product from being deformed by rapid dehydration and to prevent cracks from occurring, and to perform efficient drying. Since the inside of the molded product is particularly difficult to dry, if it is dried to some extent, it is dried in a thermostat at 50 to 200 ° C or vacuum dried, or the center of the molded product that is kept in water by microwave using a microwave oven or the like is heated. However, the water retention is desirably 0.5% by weight or less.

The ceramic casting after drying is
At 1200 to 2200 ° C depending on the type of ceramics,
Calcination is performed in the air, in an inert or reducing atmosphere, or under reduced pressure. If necessary, pressure sintering may also be required.

[0026]

The present invention will be specifically described below with reference to the following examples. However, the present invention is not limited to this.

Example 1 (Ceramic Slurry Composition) (1) Yttria partially stabilized zirconia to which 2.75 mol% ZrO _{2 of} inorganic powder Y ₂ O ₃ was added was prepared to have an average particle size of 0.12 μm. Was used as a raw material powder. To the above powder, 0.375% by weight of Al ₂ O ₃ was added as a sintering aid.

(2) Binder Using polypropylene glycol diglycidyl ether, 5% by weight was used for 100 g of powder.

(3) Dispersant A polyacrylic acid surfactant was used in an amount of 1% by weight based on 100 g of the powder.

(4) Solvent Pure water was used in an amount of 40% by weight based on 100 g of the powder.

The above-mentioned raw materials (1) to (4) are
The mixture was mixed at 0 revolutions / minute for 24 hours.

(Preparation method of cast molding) 1- (2-aminoethyl) piperazine is added as a hardening agent to the above slurry at a weight ratio of 5: 1 to the binder, and further added to a ball mill. For 5 minutes.

The stirred slurry was transferred to a glass container, sufficiently degassed under reduced pressure, poured into a mold and dried.

The mold was a non-water-absorbing material made of polypropylene resin, and was dried while controlling the humidity at room temperature to a humidity of 70%.

(Drying and sintering method) After curing to some extent, the molded body was taken out of the mold and dried. Drying at humidity 75
% At normal temperature in an atmosphere humidified so as to be%. By this drying, the cake-like mass became a strong molded body.

The compact was fired in an electric furnace in the atmosphere. The firing temperature was 1400 ° C. for 2 hours.

(Evaluation of Sintered Body) The structure of the sintered body was observed with a scanning electron microscope, and it was confirmed that the crystal grain size was 0.3 μm. Further, it was a tetragonal zirconia substantially free from cubic crystals by X-ray diffraction, and the sintered body density by Archimedes method was 6.06 g / cubic centimeter.

[0038]

According to the present invention, there is provided a technique which does not gel at the time of preparation, has excellent fluidity even at room temperature, and can be applied not only to casting, but also to injection molding, sheet molding, extrusion molding and the like. After filling into the mold and reaction-hardening, no cracks due to flow marks or shrinkage are observed, and the releasability is good. This is an excellent ceramic molding method.

Claims (7)

[Claims] When casting ceramics,
A method for producing a ceramic molded body, comprising using a crosslinkable water-soluble binder. 2. 100 parts by weight of ceramic powder,
2. The method according to claim 1, wherein 15 to 70 parts by weight of water is used.
The method for producing a ceramic molded body according to the above. 3. The casting mold for ceramics according to claim 1, wherein a casting mold having no water absorption is used.
The method for producing a ceramic molded body according to the above. 4. The method for producing a ceramic molded body according to claim 1, wherein the ceramic molded body is dried in an atmosphere having a relative humidity of 40% or more. 5. The method for producing a ceramic molded body according to claim 1, wherein the cast molded body of the ceramic is sintered under pressure. 6. The method according to claim 1, wherein the cross-linkable water-soluble binder is mainly composed of a cross-linked body containing an epoxy resin and an amine compound. 7. The method according to claim 6, wherein the polyacrylic acid-based dispersant is contained in an amount of 0.1 to 5% by weight based on 100 parts by weight of the ceramic powder.